They gathered at beach resorts in Dubai, pubs in London, and a noisy cafe in Beijing. Here in New York, they flocked to a popular West Side bar. By the time the sun set on the first annual Twestival, some 10,000 attendees in 200 cities across the globe had donated more than a quarter of million dollars to clean-water efforts in Africa and India.

Welcome to the age of “social giving.” Spurred on by the success of Barack Obama’s presidential campaign, campaigns like the Twestival, which was organized on the microblogging platform Twitter, are changing the landscape of modern philanthropy, say industry insiders. Out go the traditional fundraisers, with their extraneous marketing costs and rolls of red tape. In comes a new wave of digital efforts – often engineered by the same young activists that sealed Mr. Obama’s election.

“There’s a huge surge going on here,” says Allison Fine, author of “Momentum: Igniting Social Change in the Connected Age,” and a senior fellow at Demos, a public policy think-tank in New York. “On one hand, as large numbers of people come to social networks, from Facebook to MySpace, causes will come into the conversation. It’s part of the genetic makeup of Americans to share their passion for causes.”

On the other hand, Ms. Fine continues, “You’ve got the technological ease of creating social networks. It’s not difficult anymore to create that networking function. The only difficulty is in creating the critical mass.”

The Twestival, which wrapped on Feb. 12, had little trouble generating buzz. Only hours after founder Amanda Rose made public her plans for the campaign in January, the news went viral, spiraling out across hundreds of blogs and Twitter feeds. Soon, Ms. Rose had secured a small army of volunteers and a team of corporate partners including TipJoy, which allowed users to contribute directly online.

“There’s an older mentality when it comes to fundraising, which is, ‘give it to me now,’ ” says Beth Kanter, a new-media consultant and blogger who has written extensively on the Twestival. “But that’s not good fundraising. When you leverage a social network, you can launch smaller, employ the best practices, and gain trust.”

Ms. Kanter has raised hundreds of thousands of dollars for charity using her blog and a range of social networks, including Twitter. She says that many traditional nonprofits have been slow to adapt to the realities of the Digital Age. They hold out their coffers, and wait for the money to arrive, without realizing that an effective campaign is built carefully and incrementally using preexisting online groups.

“There’s a new breed of social citizen out there,” argues Fine, who writes a well-trafficked blog about the intersection of social media and activism. “I’m speaking here about millennials – the 15- to 29-year olds, for whom one of the key identifiers is a cause. A cause says something about who you are and who your friends are.” On Facebook, for instance, a user might join a group devoted to ecological preservation efforts in the Florida Everglades.

The savviest nonprofits will tap into these groups and cultivate relationships with activists. Peter Panepeto, who tracks online charity efforts for the Chronicle of Philanthropy, says two sites have been particularly successful at drawing Web traffic. The first is Change.org – a sprawling “social action network” founded in 2007. The second is Kiva.org, which allows users to give directly to needy individuals.

Both sites, Mr. Panepeto says, take advantage of Web 2.0 tools, from blogs to video to interactive databases. “Certainly all the trends we’re seeing point to the fact that we’ll see more sites like this springing up,” he says. The questions are whether they’ll stick around, whether people will keep coming back to them, and whether these sites will rest alongside existing technology or supplant it.

This last point, Fine and others say, is of vital importance. In the past few years, more than a few charity-oriented social networks have come and gone, mostly on the strength of their compatibility with other platforms. At a time when users expect a stripped-down simplicity from a website, many are loath to shuttle back and forth between a handful of sites, even if the cause is important. They want synergy, Fine says, and connectivity.

Furthermore, the proliferation of online giving campaigns could engender in some cases a sort of “cause fatigue. We’re marinating in causes,” Fine says. Nonprofits will have to find a way to distinguish themselves amid a gaggle of similar organizations; networks, meanwhile, will have to offer users superior functionality.

One new site navigating the online giving space is ActiveCause, which was founded by former consultant Craig Alberino.

ActiveCause differs from Change.org, for instance, in its interface and its mission. When the site is fully launched this month, potential donors will not only be able to interact with one another, but also to track the giving patterns of major corporations.

“A Fortune 500 company might give away $50 million over the course of a year,” Mr. Alberino says, “and it’s difficult in some cases to understand where that money went and who it was given away to.”

ActiveCause, he says, will make it easier for users to understand the philanthropic processes on a corporate level, and to direct their funds accordingly. It will also allow users to seamlessly pass on funds earned through programs such as Recycle Bank, which rewards eco-friendly behavior.

Conversely, Alberino hopes that ActiveCause will allow nonprofits to reach new audiences and to cater directly to users.

“A nonprofit is a business like any other,” he says. “Nonprofits need to market to their constituents, they need to understand their audience, they need tools in order to execute [effectively].”